Mobile wireless communications device having improved RF immunity of audio transducers to electromagnetic interference (EMI)

ABSTRACT

A mobile wireless communications device includes a housing and circuit board carried by the housing and having radio frequency (RF) circuitry and a processor operative with each other. Audio circuitry is carried by the circuit board and an audio transducer assembly, such as a speaker, has electrical contacts that electrically engage the audio circuitry for carrying audio signals between the audio circuitry and audio transducer assembly. A filter is mounted at the audio transducer assembly and reduces radio frequency (RF) electromagnetic interference to the audio transducer assembly during device operation.

This application is a continuation of Ser. No. 13/073,293 filed Mar. 28,2011 now U.S. Pat. No. 8,099,142 issued Jan. 17, 2012, which, in turn,is a continuation of Ser. No. 12/025,837 filed Feb. 5, 2008 now U.S.Pat. No. 7,974,582 issued Jul. 5, 2011, which, in turn, is acontinuation of Ser. No. 11/098,275 filed Apr. 4, 2005 now U.S. Pat. No.7,353,041 issued Apr. 1, 2008, all of which are hereby incorporatedherein in their entireties by reference.

FIELD OF THE INVENTION

The present invention relates to the field of communications devices,and more particularly, to mobile wireless communications devices andrelated methods.

BACKGROUND OF THE INVENTION

Cellular communication systems continue to grow in popularity and havebecome an integral part of both personal and business communications.Cellular telephones allow users to place and receive phone calls mostanywhere they travel. Moreover, as cellular telephone technology isincreased, so too has the functionality of cellular devices. Forexample, many cellular devices now incorporate Personal DigitalAssistant (PDA) features such as calendars, address books, task lists,calculators, memo and writing programs, etc. These multi-functiondevices usually allow users to wirelessly send and receive electronicmail (email) messages and access the Internet via a cellular networkand/or a wireless local area network (WLAN), for example.

As the functionality of cellular communications devices increases, thedemand increases for smaller devices that are easier and more convenientfor users to carry. As any circuit boards and electronic componentsthereon are reduced in size and placed closer together, includingantenna and microphone components, various electronic components pick-upconductive energy and create interference within the system. Forexample, an internal audio transducer, for example, a receiver speaker,such as a speaker surface mounted on the circuit board, could pick-upconducted energy directly from a power amplifier, from the radiatedenergy emitted by an antenna or from other circuitry and, as a result,create an audible buzz within the speaker. This unwanted reception ofconducted/near field radiated energy from any power amplifiers, antennaeand RF or other circuitry is particularly problematic in a packet bursttransmission as part of a Global System for Mobile communications (GSM)system including the 450 MHz, 900 MHz, 1800 MHz and 1900 MHz frequencybands. Other interfering signals that could create an audible buzz inthe speaker could be generated when the liquid crystal display (LCD) insome mobile wireless communications devices radiates radio frequency(RF) interfering energy. Interfering energy could also be generated bythe microprocessor or another similar central processing unit (CPU).

Other problems occur when the antenna impendence match is detuned andantenna gain is degraded by the coupling of adjacent electroniccomponents, for example, the receiver speaker relative to the antenna.It would be desirable to improve antenna performance of the mobilewireless communications device by blocking RF current from being coupledto the ground plane of the printed circuit board through adjacentelectronic components. For example, the receiver is typically locatedclose to the antenna and couples RF energy from the antenna to theground plane, detuning an antenna impedance match and degrading antennagain.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the detailed description of the invention whichfollows, when considered in light of the accompanying drawings in which:

FIG. 1 is a schematic block diagram of an example of a mobile wirelesscommunications device configured as a handheld device that can be usedwith the present invention and illustrating basic internal componentsthereof.

FIG. 2 is a front elevation view of the mobile wireless communicationsdevice of FIG. 1.

FIG. 3 is a schematic block diagram showing basic functional circuitcomponents that can be used in the mobile wireless communications deviceof FIGS. 1-2.

FIG. 4 is a schematic circuit diagram of an audio circuit operative withan RF circuit in the mobile wireless communications device of FIGS. 1-3,and incorporating RF filters applied to the audio transducer, such asthe illustrated receiver speaker, in accordance with the presentinvention.

FIG. 5 is a schematic circuit diagram of another embodiment of an audiocircuit similar to FIG. 4, but having a different circuit footprint.

FIG. 6 is an enlarged view of the speaker section in the schematiccircuit diagram of FIG. 4, and showing in detail RF filters locatedwithin the audio transducer housing.

FIG. 7 is a schematic circuit diagram similar to FIG. 6, but showing theRF filters located outside the audio transducer housing and seriallyconnected within audio connection lines.

FIG. 8 is a schematic circuit diagram similar to FIG. 6 and showing theRF coupling between the speaker and antenna, which is attenuated by theRF filter contained within the audio transducer housing.

FIG. 9 is a schematic circuit diagram similar to FIG. 7 and showing theRF coupling between the speaker and antenna, which is attenuated by theRF filter outside the audio transducer housing and serially connectedwithin audio connection lines.

FIG. 10 is a fragmentary, side elevation and sectional view of a speakerthat could be used in the circuits shown in FIGS. 1-9, and showingpossible locations of the RF filter in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout, and prime notation is used toindicate similar elements in alternative embodiments.

The RF filter of the invention targets the audio buzz problem created byRF electromagnetic interference on mobile wireless audio transducers,such as a receiver speaker. The RF filter is operative with the audiotransducer, for example, attached to the transducer housing, to thetransducer electrical contacts, such as resilient (spring) pads, or tothe audio circuitry, for example, the audio connection lines, e.g., thesignal traces leading to the audio transducer. The RF filter could be RFferrite beads, serially connected inductors, or shunt capacitors toreduce the RV energy that is picked-up by the transducer. Energy iscoupled to the non-linear circuit that could rectify the RF energy. Inanother aspect, an isolation RF shield as a “can” could surround andisolate the speaker from radiated energy.

In another aspect of the present invention, RF current is blocked frombeing coupled to the ground plane of the printed circuit board via theelectronic components that are located close to an antenna, thusimproving the antenna performance. For example, in some wireless mobilecommunications devices, the audio transducer, e.g., the receiverspeaker, is located close to the antenna and couples RF energy from theantenna to the ground plane. This detunes the antenna impedance anddegrades antenna gain. The RF filters can also be added serially to bothends of the speaker, which have a low DC resistance to allow normaloperation of the speaker, but high impedance over 500 MHz and up to 3GHz. The addition of the RV filter can block the RF current from beingcoupled to the ground plane and other circuitry on the printed circuitboard and decouple the antenna from any adjacent electronic components.In this manner, the antenna performance is maintained, for example,maintaining impedance match and antenna gain.

A mobile wireless communications device of the present inventionincludes a housing and circuit board carried by the housing andincluding radio frequency (RF) circuitry and a processor operative witheach other. Audio circuitry is carried by the circuit board andoperative with the RF circuitry and processor. An audio transducerassembly, such as a receiver speaker, is carried by the circuit boardand has electrical contacts that electrically engage the audio circuitryfor carrying audio signals between the audio circuitry and audiotransducer assembly. A filter is mounted at the audio transducerassembly and reduces the radio frequency (RF) electromagneticinterference to the audio transducer assembly during device operation.

In one aspect of the invention, the filter could be an RF shield or“can” that surrounds or encloses all or a portion of the transducer, ora ferrite bead, serial inductor, or bypass capacitor connected to signallines of the transducer. The audio circuitry could include a receiveraudio switch and audio connection lines carried by the circuit boardthat interconnect the RF circuitry, processor and receiver audio switch.The transducer, e.g., speaker, can be surface mounted on the circuitboard and has electrical contacts that electrically engage the audiocircuitry for carrying the audio signals between the audio circuitry andtransducer. The filter can be serially connected between the audiocircuitry and the electrical contact of the transducer. In one aspect ofthe present invention, the audio transducer includes a transducerhousing with the filter positioned within the audio transducer housing.The electrical contacts can be formed as resilient or “spring” contactpads that engage the audio circuitry.

In another aspect of the present invention, the filter can be locatedbetween the audio transducer housing and resilient contact pads. Thefilter could be formed as a surface mounted device positioned adjacentthe electrical contacts and engaging the audio circuitry.

A brief description will now proceed relative to FIGS. 1-3, whichdisclose an example of a mobile wireless communications device, forexample, a handheld portable cellular radio, which can incorporate thenon-limiting examples of the various circuits of the present invention.FIGS. 1-3 are representative non-limiting examples of the many differenttypes of functional circuit components and their interconnection, andoperative for use with the present invention.

Referring initially to FIGS. 1 and 2, an example of a mobile wirelesscommunications device 20, such as a handheld portable cellular radio,which can be used with the present invention is first described. Thisdevice 20 illustratively includes a housing 21 having an upper portion46 and a lower portion 47, and a dielectric substrate (i.e., circuitboard) 67, such as a conventional printed circuit board (PCB) substrate,for example, carried by the housing. A housing cover (not shown indetail) would typically cover the front portion of the housing. The termcircuit board 67 as used hereinafter can refer to any dielectricsubstrate, PCB, ceramic substrate or other circuit carrying structurefor carrying signal circuits and electronic components within the mobilewireless communications device 20. The illustrated housing 21 is astatic housing, for example, as opposed to a flip or sliding housingwhich are used in many cellular telephones. However, these and otherhousing configurations may also be used.

Circuitry 48 is carried by the circuit board 67, such as amicroprocessor, memory, one or more wireless transceivers (e.g.,cellular, WLAN, etc.), which includes RF circuitry, including audio andpower circuitry, including any keyboard circuitry. It should beunderstood that keyboard circuitry could be on a separate keyboard,etc., as will be appreciated by those skilled in the art. A battery (notshown) is also preferably carried by the housing 21 for supplying powerto the circuitry 48. The term RF circuitry could encompass theinteroperable RF transceiver circuitry, power circuitry and audiocircuitry.

Furthermore, an audio output transducer 49 (e.g., a speaker) is carriedby an upper portion 46 of the housing 21 and connected to the circuitry48. One or more user input interface devices, such as a keypad(keyboard) 23 (FIG. 2), is also preferably carried by the housing 21 andconnected to the circuitry 48. The term keypad as used herein alsorefers to the term keyboard, indicating the user input devices havinglettered and/or numbered keys commonly known and other embodiments,including multi-top or predictive entry modes. Other examples of userinput interface devices include a scroll wheel 37 and a back button 36.Of course, it will be appreciated that other user input interfacedevices (e.g., a stylus or touch screen interface) may be used in otherembodiments.

An antenna 45 is preferably positioned at the lower portion 47 in thehousing and can be formed as a pattern of conductive traces that make anantenna circuit, which physically forms the antenna. It is connected tothe circuitry 48 on the main circuit board 67. In one non-limitingexample, the antenna could be formed on an antenna circuit board sectionthat extends from the main circuit board at the lower portion of thehousing. By placing the antenna 45 adjacent the lower portion 47 of thehousing 21, the distance is advantageously increased between the antennaand the user's head when the phone is in use to aid in complying withapplicable SAR requirements. Also, a separate keyboard circuit boardcould be used.

More particularly, a user will typically hold the upper portion of thehousing 21 very close to his head so that the audio output transducer 49is directly next to his ear. Yet, the lower portion 47 of the housing 21where an audio input transducer (i.e., microphone) is located need notbe placed directly next to a user's mouth, and can be held away from theuser's mouth. That is, holding the audio input transducer close to theuser's mouth may not only be uncomfortable for the user, but it may alsodistort the user's voice in some circumstances. In addition, theplacement of the antenna 45 adjacent the lower portion 47 of the housing21 also advantageously spaces the antenna farther away from the user'sbrain.

Another important benefit of placing the antenna 45 adjacent the lowerportion 47 of the housing 21 is that this may allow for less impact onantenna performance due to blockage by a user's hand. That is, userstypically hold cellular phones toward the middle to upper portion of thephone housing, and are therefore more likely to put their hands oversuch an antenna than they are an antenna mounted adjacent the lowerportion 47 of the housing 21. Accordingly, more reliable performance maybe achieved from placing the antenna 45 adjacent the lower portion 47 ofthe housing 21.

Still another benefit of this configuration is that it provides moreroom for one or more auxiliary input/output (I/O) devices 50 to becarried at the upper portion 46 of the housing. Furthermore, byseparating the antenna 45 from the auxiliary I/O device(s) 50, this mayallow for reduced interference therebetween.

Some examples of auxiliary I/O devices 50 include a WLAN (e.g.,Bluetooth, IEEE 802.11) antenna for providing WLAN communicationcapabilities, and/or a satellite positioning system (e.g., GPS, Galileo,etc.) antenna for providing position location capabilities, as will beappreciated by those skilled in the art. Other examples of auxiliary I/Odevices 50 include a second audio output transducer (e.g., a speaker forspeaker phone operation), and a camera lens for providing digital cameracapabilities, an electrical device connector (e.g., USB, headphone,secure digital (SD) or memory card, etc.).

It should be noted that the term “input/output” as used herein for theauxiliary I/O device(s) 50 means that such devices may have input and/oroutput capabilities, and they need not provide both in all embodiments.That is, devices such as camera lenses may only receive an opticalinput, for example, while a headphone jack may only provide an audiooutput.

The device 20 further illustratively includes a display 22, for example,a liquid crystal display (LCD) carried by the housing 21 and connectedto the circuitry 48. A back button 36 and scroll wheel 37 can also beconnected to the circuitry 48 for allowing a user to navigate menus,text, etc., as will be appreciated by those skilled in the art. Thescroll wheel 37 may also be referred to as a “thumb wheel” or a “trackwheel” in some instances. The keypad 23 illustratively includes aplurality of multi-symbol keys 24 each having indicia of a plurality ofrespective symbols thereon. The keypad 23 also illustratively includesan alternate function key 25, a next key 26, a space key 27, a shift key28, a return (or enter) key 29, and a backspace/delete key 30.

The next key 26 is also used to enter a “*” symbol upon first pressingor actuating the alternate function key 25. Similarly, the space key 27,shift key 28 and backspace key 30 are used to enter a “0” and “#”,respectively, upon first actuating the alternate function key 25. Thekeypad 23 further illustratively includes a send key 31, an end key 32,and a convenience (i.e., menu) key 39 for use in placing cellulartelephone calls, as will be appreciated by those skilled in the art.

Moreover, the symbols on each key 24 are arranged in top and bottomrows. The symbols in the bottom rows are entered when a user presses akey 24 without first pressing the alternate function key 25, while thetop row symbols are entered by first pressing the alternate functionkey. As seen in FIG. 2, the multi-symbol keys 24 are arranged in thefirst three rows on the keypad 23 below the send and end keys 31, 32.Furthermore, the letter symbols on each of the keys 24 are arranged todefine a QWERTY layout. That is, the letters on the keypad 23 arepresented in a three-row format, with the letters of each row being inthe same order and relative position as in a standard QWERTY keypad.

Each row of keys (including the fourth row of function keys 25-29) isarranged in five columns. The multi-symbol keys 24 in the second, third,and fourth columns of the first, second, and third rows have numericindicia thereon (i.e., 1 through 9) accessible by first actuating thealternate function key 25. Coupled with the next, space, and shift keys26, 27, 28, which respectively enter a “*”, “0”, and “#” upon firstactuating the alternate function key 25, as noted above, this set ofkeys defines a standard telephone keypad layout, as would be found on atraditional touch-tone telephone, as will be appreciated by thoseskilled in the art.

Accordingly, the mobile wireless communications device 20 as describedmay advantageously be used not only as a traditional cellular phone, butit may also be conveniently used for sending and/or receiving data overa cellular or other network, such as Internet and email data, forexample. Of course, other keypad configurations may also be used inother embodiments. Multi-tap or predictive entry modes may be used fortyping e-mails, etc. as will be appreciated by those skilled in the art.

The antenna 45 is preferably formed as a multi-frequency band antenna,which provides enhanced transmission and reception characteristics overmultiple operating frequencies. More particularly, the antenna 45 isdesigned to provide high gain, desired impedance matching, and meetapplicable SAR requirements over a relatively wide bandwidth andmultiple cellular frequency bands. By way of example, the antenna 45preferably operates over five bands, namely a 850 MHz Global System forMobile Communications (GSM) band, a 900 MHz GSM band, a DCS band, a PCSband, and a WCDMA band (i.e., up to about 2100 MHz), although it may beused for other bands/frequencies as well. To conserve space, the antenna45 may advantageously be implemented in three dimensions although it maybe implemented in two-dimensional or planar embodiments as well.

The mobile wireless communications device shown in FIGS. 1 and 2 canincorporate e-mail and messaging accounts and provide differentfunctions such as composing e-mail, PIN messages, and SMS messages. Thedevice can manage messages through an appropriate menu that can beretrieved by choosing a messages icon. An address book function couldadd contacts, allow management of an address book, set address bookoptions and manage SIM card phone books. A phone menu could allow forthe making and answering of phone calls using different phone features,managing phone call logs, setting phone options, and viewing phoneinformation. A browser application could permit the browsing of webpages, configuring a browser, adding bookmarks, and changing browseroptions. Other applications could include a task, memo pad, calculator,alarm and games, as well as handheld options with various references.

A calendar icon can be chosen for entering a calendar program that canbe used for establishing and managing events such as meetings orappointments. The calendar program could be any type of messaging orappointment/meeting program that allows an organizer to establish anevent, for example, an appointment or meeting.

A non-limiting example of various functional components that can be usedin the exemplary mobile wireless communications device 20 of FIGS. 1 and2 is further described in the example below with reference to FIG. 3.The device 20 illustratively includes a housing 120, a keypad 140 and anoutput device 160. The output device 160 shown is preferably a display,which is preferably a full graphic LCD. Other types of output devicesmay alternatively be used. A processing device 180 is contained withinthe housing 120 and is coupled between the keypad 140 and the display160. The processing device 180 controls the operation of the display160, as well as the overall operation of the mobile device 20, inresponse to actuation of keys on the keypad 140 by the user.

The housing 120 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 180, other parts of the mobiledevice 20 are shown schematically in FIG. 3. These include acommunications subsystem 101; a short-range communications subsystem102; the keypad 140 and the display 160, along with other input/outputdevices 106, 108, 110 and 112; as well as memory devices 116, 118 andvarious other device subsystems 121. The mobile device 20 is preferablya two-way RF communications device having voice and data communicationscapabilities. In addition, the mobile device 20 preferably has thecapability to communicate with other computer systems via the Internet.

Operating system software executed by the processing device 180 ispreferably stored in a persistent store, such as the flash memory 116,but may be stored in other types of memory devices, such as a read onlymemory (ROM) or similar storage element. In addition, system software,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store, such as the random access memory (RAM)118. Communications signals received by the mobile device may also bestored in the RAM 118.

The processing device 180, in addition to its operating systemfunctions, enables execution of software applications 130A-130N on thedevice 20. A predetermined set of applications that control basic deviceoperations, such as data and voice communications 130A and 130B, may beinstalled on the device 20 during manufacture. In addition, a personalinformation manager (PIM) application may be installed duringmanufacture. The PIM is preferably capable of organizing and managingdata items, such as e-mail, calendar events, voice mails, appointments,and task items. The PIM application is also preferably capable ofsending and receiving data items via a wireless network 141. Preferably,the PIM data items are seamlessly integrated, synchronized and updatedvia the wireless network 141 with the device user's corresponding dataitems stored or associated with a host computer system.

Communication functions, including data and voice communications, areperformed through the communications subsystem 101, and possibly throughthe short-range communications subsystem. The communications subsystem101 includes a receiver 150, a transmitter 152, and one or more antennae154 and 156. In addition, the communications subsystem 101 also includesa processing module, such as a digital signal processor (DSP) 158, andlocal oscillators (LOS) 161. The specific design and implementation ofthe communications subsystem 101 is dependent upon the communicationsnetwork in which the mobile device 20 is intended to operate. Forexample, the mobile device 20 may include a communications subsystem 101designed to operate with the Mobitex™, Data TAC™ or General Packet RadioService (GPRS) mobile data communications networks, and also designed tooperate with any of a variety of voice communications networks, such asAMPS, TDMA, CDMA, PCS, GSM, etc. Other types of data and voice networks,both separate and integrated, may also be utilized with the mobiledevice 20.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore requires a subscriber identitymodule, commonly referred to as a SIM card, in order to operate on aGPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 20 may send and receive communicationssignals over the communication network 141. Signals received from thecommunications network 141 by the antenna 154 are routed to the receiver150, which provides for signal amplification, frequency down conversion,filtering, channel selection, etc., and may also provide analog todigital conversion. Analog-to-digital conversion of the received signalallows the DSP 158 to perform more complex communications functions,such as demodulation and decoding. In a similar manner, signals to betransmitted to the network 141 are processed (e.g., modulated andencoded) by the DSP 158 and are then provided to the transmitter 152 fordigital to analog conversion, frequency up conversion, filtering,amplification and transmission to the communication network 141 (ornetworks) via the antenna 156.

In addition to processing communications signals, the DSP 158 providesfor control of the receiver 150 and the transmitter 152. For example,gains applied to communications signals in the receiver 150 andtransmitter 152 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 158.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 101and is input to the processing device 180. The received signal is thenfurther processed by the processing device 180 for an output to thedisplay 160, or alternatively to some other auxiliary I/O device 106. Adevice user may also compose data items, such as e-mail messages, usingthe keypad 140 and/or some other auxiliary I/O device 106, such as atouchpad, a rocker switch, a thumb-wheel, or some other type of inputdevice. The composed data items may then be transmitted over thecommunications network 141 via the communications subsystem 101.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 110, and signals fortransmission are generated by a microphone 112. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 20. In addition, the display 160 mayalso be utilized in voice communications mode, for example to displaythe identity of a calling party, the duration of a voice call, or othervoice call related information.

Any short-range communications subsystem enables communication betweenthe mobile device 20 and other proximate systems or devices, which neednot necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, or a Bluetooth™ communications module toprovide for communication with similarly-enabled systems and devices.

FIG. 4 shows a basic audio circuit 200, including serial bus connectionsthat can be used for mobile wireless communications device 20 shown inFIGS. 1-3, and includes an audio transducer, such as the receiverspeaker 206. FIGS. 6-9 illustrate different RF components added into ornear the receiver speaker 206, in accordance with the invention. Thisaudio circuit 200 also has certain types of values of filters placedaround the device to reduce immunity.

Basic audio components are shown in the dashed rectangular box andinclude two microphone audio switches 202, which include a headsetdetect circuit 204 that is triggered when the headset jack has anexternal speaker microphone connected thereto. It detects the microphoneand switches the lines over. At the audio transducer assembly,hereinafter referred to as the receiver speaker or speaker 206, are twospeaker audio switches 210, each with a detect circuit 212 that detectswhen an earphone is connected to switch the line over. An inductorcomponent 214 as a filter is operative with the receiver speaker 206 andthe audio switches 210. As shown in greater detail in the enlargedschematic circuit diagrams in FIGS. 6-9, different resistor 216,capacitor 217 and terminals 218 are operatively connected to switches210.

An example of the audio switch could be a 0.5 ohm/0.8 ohm low-voltage,dual single-pole/double-throw (SPDT) analog switch that could operatefrom a single 1.8 volt to 5.5 volt supply. An example of such a switchis the Maxim 4684 and 4685, low-on resistance (R on) switches. Theseswitches are packaged in a chip scale package (UCSP) that reduces therequired printed circuit board area. A chip of this type typicallyoccupies about 2.0 mm by 1.50 mm area. A 4×3 array of solder bumps canbe spaced with a 0.5 mm bump pitch. Proper power-supply sequencing wouldtypically be required for CMOS devices. The different pins could includea normally closed terminal pin, a digitally controlled input pin, ananalog switch, common terminal pin, an analog switch normally openterminal pin, a positive supply voltage input pin, and a ground pin.

The receiver speaker could be a 28 mm speaker such as the type WD11903by Phillips Speaker Systems. It is typically formed with a frame/volumeof ABS/SAN, and a cone formed from polycarbonate (PC). The cone colorcould be yellow transparent and the weight is about 4.9 grams. Thediameter is 28 mm. The magnet could be formed from NdFeB material and isabout 12 mm. The speaker could include a resilient contact pad forming aspring-contact connection, and a parallel ZU PCB gasket and a PC RING.This type of speaker could operate at a range of about 560 Hz to 5,000Hz and typically within the voice range. It would have a resonantfrequency of about 700 Hz and a voice coil resistance of about 7.3 Ohms.It could use about 1 watt maximum short term power and a maximum noisepower of about 0.5 watts continuous.

To provide the speaker 206 with RF isolation, FIG. 4 shows that a radiofrequency isolation shield 206 a can form an isolation “can,” i.e., anisolation compartment at that area of the circuit board in which thespeaker is mounted. This RF shield 206 a could be formed as a separatemetallic housing secured to the circuit board and surrounding thespeaker, effectively covering, i.e., shielding the entire speaker.Naturally, some porous holes could be provided to allow sound to escape.Although a “can” configuration formed as a metallic housing with top andsides can be used for, the RF shield 206 a, other configurations couldbe used. The receiver is typically and preferably, in one aspect, asurface mounted receiver such as the receiver speaker described above.This RF shield provides the necessary isolation from the RF amplifiers,power circuitry, radiated antenna energy, and other interfering RFenergy that could create an audible buzz within the speaker.

In another aspect of the invention described below, the RF filter couldbe ferrite beads, bypass capacitors, or serial inductors and placedwithin the speaker housing or outside the speaker and connected into theaudio connection lines. It should be understood that the term “speaker”could also be synonymous with any type of audio transducer assembly thatis carried by the housing of the wireless communications device, buttypically mounted on the circuit board.

Different types, sizes and shapes of ferrite beads can be used.Typically, a ferrite bead is formed from a material having apermeability controlled by the composition of the different oxides, forexample, a ferric oxide, sometimes with nickel and zinc added. Theferrite beads can sometimes be formed as ferrite sleeves with two halfparts that are added onto a signal line or a solder overcoat on a signaltrace. Typically, the longer the bead, the better the RF suppression.The bead equivalent circuit can be a series resistor and inductor.

A physical jack is indicated at 220 and receives a jack input andconnects to headset detect line and terminal 221, which also includes aserially connected inductor 222. The described components are connectedtogether and operative with the microprocessor and other components, forexample, various inductors, diodes, capacitors, resistors, andassociated circuit components.

To increase the immunity (i.e., reduce the susceptibility) of the device20 to electromagnetic interference (EMI), a plurality of EMI filters areadded to the audio and/or serial bus circuit 200 of the communicationsdevice 20. As shown in FIG. 4, for example, choke filters (i.e.,inductors) can include respective individual inductors for this purpose.A choke filter 240 is operatively connected into connection line 242between the physical jack 220 and the microprocessor 180. Thisconnection line 242 includes a capacitor circuit 244. Another chokefilter 250 is operatively connected to the microphone audio switches202. Yet another choke filter 260 is operatively connected to thephysical jack 220 and the microprocessor 180 on a connection line 262.Although the inductor or choke filters as illustrated and positioned inthe respective selected circuit positions, it should be understood thatother filters can be used for the present invention.

Other basic components included in FIG. 4 include the test points 270near the receiver speaker 206.

FIG. 5 is a schematic circuit diagram for an audio circuit 280 similarto that shown in FIG. 4, including serial bus connections and havinganother circuit footprint, such as for a mobile wireless communicationsdevice 20, and showing similar components in a different configuration.Any similar components have been given the same reference numeral. Thiscircuit 280 also includes an operational amplifier circuit 281operatively connected to the microprocessor 180 and operative as afilter or buffer. FIG. 5 also shows a microphone circuit 282, whichwould be operative with microphone audio switches 202, even though inthis fragmentary schematic circuit diagram it is shown separate. Chokefilter 283 is operatively connected to the microphone circuit 282. Achoke filter 284 is operatively connected to the physical jack 220 andthe operational amplifier circuit 281. Another choke filter 285 isoperatively connected to a microphone audio switch 202. Other circuitcomponents can be connected as illustrated in this non-limiting example.

The choke filters are advantageously used at the frequency band about 40MHz, which has a strong impact on the immunity performance of the radio.Critical spots are selectively chosen for these ESP filters designed inthese examples as choke filters. A capacitor circuit 286 is connectedbetween operational amplifier 281 and input jack 220 for determiningconnection. A transistor circuit 286 a is included in this design andoperatively connected between the operational amplifier circuit 281 andinto connection lines for the filter 284 and input jack 220. The circuit280 includes other components that are connected as illustrated in thisnon-limiting example.

By way of example, the choke filters as described with reference toFIGS. 4 and 5 could be ferrite filters, for example, ferrite beads,although other suitable filter components and/or materials may also beused, as will be appreciated by those skilled in the art. In addition topositioning the EMI filters to reduce unwanted interference, othercomponents connected to the audio and/or serial bus circuitry can bescrutinized to determine if interference susceptibility effects.

The use of the added choke filters advantageously reduces conductedinterfering energy introduced to the audio components via a serial(i.e., USB) charging cable and other sources. This further reducesradiated interfering RF energy introduced to the audio components viathe microphone 112 (FIG. 3) or the microphone of a connected headset,for example.

As illustrated in FIG. 10, the transducer, e.g., the speaker in thisexample, includes a speaker housing 206 b. The various components of thespeaker as described above are contained in the housing. Othercomponents could include an electrical contact 206 c that engages theaudio circuitry, such as the audio connection lines. The contact istypically formed as a spring contact having a contact pad member 206 d.The enlarged view also shows that any contact pad 206 d is surfacemounted on the circuit board 67. The RF ground plane 67 a is shownpositioned on the underside of the circuit board. The pad can be formedlarge to obtain good conductive contact between the various componentsof the speaker 206 and the audio circuitry.

As illustrated, a filter 300 is mounted at the audio transducerassembly, e.g., the receiver speaker 206, and reduces the radiofrequency (RF) electromagnetic interference of the audio transducerassembly during device operation. Although the filter 300 could be an RFshield as shown in FIGS. 4 and 5, in FIGS. 6-9, the filter is a discretecomponent. As shown in FIG. 6, the filter 300 can be formed as twofilter components added serially into the “in” speaker line and “ground”speaker line and positioned within the receiver or audio transducerhousing 206 b. The filter 300 can also be serially connected within theaudio circuitry at the electrical contact and positioned outside thehousing as shown in FIG. 7. In one aspect of the invention, the speakeror transducer assembly 206 includes the resilient electrical contactpads 206 d that engage audio circuitry such as the audio signal lines orsignal traces on a circuit board 67.

FIG. 10 shows different places where the filter could be located,including on the circuit board 67 adjacent the electrical contact formedas a contact pad 206 d, between the contact pad 206 d and housing 206 b,or within the housing at an opportune location as indicated abstractlyin FIG. 10.

In one aspect of the invention, the filter 300 could be formed as aferrite bead or as a surface mounted filter device positioned adjacentthe electrical contacts and engaging the signal traces of the audioconnection lines. The filter could also be formed as a serial inductoror shunt capacitor and placed appropriately into the circuit adjacentthe speaker for maximum effect.

FIGS. 8 and 9 are similar to respective FIGS. 6 and 7, but show that theRF filter 300 is operative for improving antenna performance by blockingRF current from being coupled to the ground plane 67 a of the printedcircuit board by the close and adjacent electronic components. Thespeaker 206 can be located close to the antenna and couple RF energyfrom the antenna to the ground plane and cause antenna impedance matchdetuning and antenna gain degradation. The RF filter, such as RF EMIferrite beads 300, are serially connected to both ends of the speakerand have low DC resistance to allow normal operation of the speaker, buthave high impedance over 500 MHz up to about 3 GHz. The RF current iseffectively blocked from being coupled to the ground plane and othercircuitry on the printed circuit board and decoupling the antenna fromadjacent electronic components. Thus, the antenna performance, such asimpedance matching antenna gain is maintained by the invention.

This application is related to copending patent application entitled,“MOBILE WIRELESS COMMUNICATIONS DEVICE HAVING IMPROVED ANTENNA IMPEDANCEMATCH AND ANTENNA GAIN FROM RF ENERGY” which is filed on the same dateand by the same assignee and inventors.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

1. An electronic device comprising: at least one circuit board; radiofrequency (RF) circuitry carried by said at least circuit board; anaudio transducer assembly carried by said at least one circuit board andcomprising an audio transducer, a transducer housing for said audiotransducer, and at least one electrical contact pad member on saidtransducer housing and coupled to said audio transducer; audio circuitrycomprising at least one signal trace on said at least one circuit boardand engaging said at least one electrical contact pad member; at leastone first filter coupled with said at least one signal trace; and atleast one second filter mounted at said at least one electrical contactpad member.
 2. The electronic device according to claim 1, wherein saidat least one electrical contact pad member comprises a plurality ofresilient contact pads.
 3. The electronic device according to claim 2,wherein said at least one second filter comprises a plurality thereofconnected adjacent respective resilient contact pads.
 4. The electronicdevice according to claim 2, wherein said at least one second filtercomprises at least one ferrite bead.
 5. The electronic device accordingto claim 1, wherein said at least one second filter comprises at leastone surface mount filter.
 6. The electronic device according to claim 1,wherein said audio transducer assembly comprises a speaker within saidtransducer housing.
 7. The electronic device according to claim 1,wherein said at least one circuit board comprises an antenna circuitboard.
 8. An electronic device comprising: at least one circuit boardcarried by the housing; radio frequency (RF) circuitry carried by saidat least circuit board; an audio transducer assembly carried by said atleast one circuit board and comprising an audio transducer, a transducerhousing for said audio transducer, and at least one electrical contactpad member on said transducer housing and coupled to said audiotransducer; audio circuitry comprising at least one signal trace on saidat least one circuit board and engaging said at least one electricalcontact pad member; at least one first filter coupled with said at leastone signal trace; and at least one second filter mounted within saidtransducer housing.
 9. The electronic device according to claim 8,wherein said at least one electrical contact pad member comprises aplurality of resilient contact pads.
 10. The electronic device accordingto claim 8, wherein said at least one second filter comprises at leastone ferrite bead.
 11. The electronic device according to claim 8,wherein said at least one second filter comprises at least one surfacemount filter.
 12. The electronic device according to claim 8, whereinsaid audio transducer assembly comprises a speaker within saidtransducer housing.
 13. The electronic device according to claim 8,wherein said at least one circuit board comprises an antenna circuitboard.
 14. A method for making an electronic device comprising:providing at least one circuit board with radio frequency (RF) circuitrycarried thereby; mounting an audio transducer assembly to the at leastone circuit board and comprising an audio transducer, a transducerhousing for the audio transducer, and at least one electrical contactpad member on the transducer housing and coupled to the audiotransducer; providing audio circuitry comprising at least one signaltrace on the at least one circuit board and engaging the at least oneelectrical contact pad member; coupling at least one first filter withthe at least one signal trace; and mounting at least one second filterat the at least one electrical contact pad member.
 15. The methodaccording to claim 14, wherein the at least one electrical contact padmember comprises a plurality of resilient contact pads.
 16. The methodaccording to claim 15, wherein the at least one second filter comprisesa plurality thereof connected adjacent respective resilient contactpads.
 17. The method according to claim 14, wherein the at least onesecond filter comprises at least one ferrite bead.
 18. The methodaccording to claim 14, wherein the at least one second filter comprisesat least one surface mount filter.
 19. A method for making an electronicdevice comprising: providing at least one circuit board with radiofrequency (RF) circuitry carried thereby; mounting an audio transducerassembly to the at least one circuit board and comprising an audiotransducer, a transducer housing for the audio transducer, and at leastone electrical contact pad member on the transducer housing and coupledto the audio transducer; providing audio circuitry comprising at leastone signal trace on the at least one circuit board and engaging the atleast one electrical contact pad member; coupling at least one firstfilter with the at least one signal trace; and mounting at least onesecond filter within the transducer housing.
 20. The method according toclaim 19, wherein the at least one electrical contact pad membercomprises a plurality of resilient contact pads.
 21. The methodaccording to claim 19, wherein the at least one second filter comprisesat least one ferrite bead.
 22. The method according to claim 19, whereinthe at least one second filter comprises at least one surface mountfilter.